Several recent studies have investigated choice between cooperative and individual behavior in pairs of human Ss within an operant conditioning framework, and have isolated variables which disrupt ongoing cooperative responding. The experimental designs utilized in these studies have typically involved the establishment of a baseline which maintains cooperative responding, followed by the introduction of a disrupting stimulus (e.g., point-loss) or contingency (e.g.,inequity) sufficient to produce a shift from cooperative to individual responding. Such procedures cannot detect changes in preference that do not result in a shift between response modes, nor do they provide information about the "depth" of a shift that does occur. In the procedure to be developed, a "point of indifference" between cooperative and individual responding (a point at which the two modes of response are equally preferred) will be continuously monitored, using a technique suggested by an existing psychophysical method for tracking sensory thresholds. Variations in degree of preference for cooperative responding, including transitory ones, will be indicated by corresponding changes in the point of indifference. In addition to being far more informative than currently available procedures, such a technique promises advantages of economy by increasing the usefulness of within-S and within-session experimental designs. An investigation of the effects of payoff inequity on preference for cooperation is proposed as an initial test of the utility of the technique.